Device for use in the ultrasonic measurement of mass flow of gas

Abstract

In a device for measuring ultrasonically the flow of gas, for example the air flow in the induction duct of an internal combustion engine, an upstream piezo-electric transducer is located in a plenum chamber upstream of a measurement duct and a downstream piezoelectric transducer is located in a seating in the measurement duct. To reduce vorticity in the gas flow the upstream transducer is seated at the apex of a frusto-conical element in the inlet chamber and the seating of the downstream transducer is tapered externally.

We claim: 
     
       1. Device for the ultrasonic measurement of the flow of gas, particularly the rate of flow of air in the induction duct of an internal combustion engine, of the type comprising a measurement duct, and respective upstream and downstream piezoelectric ultrasonic transducers mounted adjacent the ends of said measurement duct adapted to provide signals for measuring flow rate, wherein the improvement consists in: - means defining a plenum chamber situated at the inlet end of the measurement duct;   - a frusto-conical element within said chamber, the vertex of which element faces towards said measurement duct,   - an upstream seating supporting the upstream transducer at the said vertex of said frusto-conical element, and   - a downstream seating supporting said downstream transducer, said downstream seating having a tapered end facing the inlet end of the said measuring duct.   
     
     
       2. The device defined in claim 1, wherein the said frusto-conical element is covered with acoustically insulating material. 
     
     
       3. The device defined in claim 1, including a sheath of elastic material interposed between each of the transducers and its respective seating.